Infusion pumps are used for treating a number of disease states requiring subcutaneous delivery of a drug. As part of the current trend towards enhanced usability, some infusion pumps are now being produced as “patch-pumps”, meaning that the long tube between a remote pump and the infusion-set on the skin is eliminated. Instead, a device with a similar footprint to the infusion-set alone constitutes the entire pump, including the drug-reservoir and the actuator which drives the drug infusion. However, even though this transition to patch-pumps represents a miniaturization of the product, typically the filling process by which the patient fills the drug reservoir remains the same and is performed at the point-of-use. Other approaches for providing the drug in a patch-pump are (a) inserting a cartridge containing the drug into the patch-pump, and (b) having a pre-filled drug reservoir integrally contained within the patch-pump already during the pump manufacturing process; said drug-reservoir thereby constituting the primary-container for the drug. Whereas the act of inserting a cartridge-type reservoir into the patch-pump can open a liquid channel from the cartridge to the cannula assembly, for a drug-reservoir that is assembled within the patch-pump, an alternative means of creating this fluid connection is required.